The features of the present invention may be used in the printing arts, and, more particularly, in digital image processing and electrophotographic printing. In digital image processing it is commonly known that various image processing operations may be applied to specific areas, or windows, of an image. It is also known that the image processing operations to be applied to individual pixels of the image may be controlled or managed by a pixel location comparison scheme. In other words, comparing the coordinate location of each pixel with a series of window coordinate boundaries to determine within which window a pixel lies. Once the window is determined, the appropriate processing operation can be defined for the digital signal at that pixel location. In general, the window identification and management systems previously employed for image processing operations have been limited to rectangularly shaped, non-overlapping windows. In the interests of processing efficiency and hardware minimization, including memory reduction, a more efficient window management system is desired: Accordingly, the present invention provides an improved method and apparatus for the management of multiple image processing operations which are to be applied to a stream of digital signals representing an image.
Previously, various approaches have been devised for the control of digital image processing and window management, of which the following disclosures appear to be relevant:
U.S. Pat. No. 4,760,463 Patentee: Nonoyama et al. Issued: Jul. 26, 1988
U.S. Pat. No. 4,780,709 Patentee: Randall Issued: Oct. 25, 1988
U.S. Pat. No. 4,887,163 Patentee: Maeshima Issued: Dec. 12, 1989
U.S. Pat. No. 4,897,803 Patentee: Calarco et al. Issued: Jan. 30, 1990
U.S. Pat. No. 4,951,231 Patentee: Dickinson et al. Issued: Aug. 21, 1990
The relevant portions of the foregoing patents may be briefly summarized as follows:
U.S. Pat. No. 4,760,463 to Nonoyama et al. discloses an image scanner including an area designating section for designating a rectangular area on an original and a scanning mode designating section for designating an image scanning mode within and outside the rectangular area designated by the area designating section. Rectangular areas are defined by designating the coordinates of an upper left corner and a lower right corner. Subsequently, counters are used for each area boundary, to determine when the pixel being processed is within a specific area.
U.S. Pat. No. 4,780,709 to Randall discloses a display processor, suitable for the display of multiple windows, in which a screen may be divided into a plurality of horizontal strips which may be a single pixel in height. Each horizontal strip is divided into one or more rectangular tiles. The tiles and strips are combined to form the viewing windows. Since the tiles may be a single pixel in width, the viewing window may be arbitrarily shaped. The individual strips are defined by a linked list of descriptors in memory, and the descriptors are updated only when the viewing windows on the display are changed. During generation of the display, the display processor reads the descriptors and fetches and displays the data in each tile without the need to store it intermediately in bit map form.
U.S. Pat. No. 4,887,163 to Maeshima discloses an image processing apparatus having a digitizing unit capable of designating desired areas in an original image and effecting the desired image editing process inside and outside the designated areas. A desired rectangular area is defined by designating two points on the diagonal corners of the desired rectangular area. During scanning, a pair of editing memories are used interchangeably to enable, first, the editing of thresholded video data from a CCD and, second, the writing of editing information for use with subsequent video data. The editing memories comprise a memory location, one byte, for each CCD element, said location holding image editing data determining the editing process to be applied to the signal generated by the respective CCD element.
U.S. Pat. No. 4,897,803 to Calarco et al., the relevant portions of which are incorporated by reference, discloses a method and apparatus for processing image data having an address designation, or token, associated with each data element, thereby identifying the element's location in an image. During processing of the image data, the address token for each data element is passed through address detection logic to determine if the address is an "address of interest," thereby signaling the application of an image processing operation.
U.S. Pat. No. 4,951,231 to Dickinson et al. discloses an image display system in which image data is stored as a series of raster scan pel definition signals in a data processor system. The position and size of selected portions of an image to be displayed on a display screen can be transformed, in response to input signals received from a controlled input device. The display device includes a control program store which stores control programs for a plurality of transform operations, such as rotation, scaling, or extraction.
The present invention seeks to overcome the limitations of the systems disclosed in the references by efficiently handling the control and management of the image processing effects selected for specific windows. The present invention also seeks to reduce the hardware complexity and/or memory requirements of such an image processing control system by reducing the amount of non-data information needed to identify the image processing operation that is to be applied to each data element.
In accordance with one aspect of the present invention, there is provided an apparatus for managing the processing of an array of digital signals representing an original image, in order to produce an array of modified digital signals. The image processing apparatus is able to operate on non-overlapping rectangular regions, or tiles, defined with respect to the input signal array, and to thereby identify image processing effects to be applied to the signals lying within the tiles. In response to the identified image processing effects defined for each signal, image processing hardware within the system is selectively enabled to process the signals.
Pursuant to another aspect of the present invention, there is provided an apparatus for managing the selection and control of the image processing effects to be applied to the image data, the apparatus having means for storing the effects within a block of memory which is accessible via an index or pointer value. The apparatus further including means for determining the effect pointer for each of a plurality of non-overlapping tile regions within the image data, and selectively enabling the image processing operations associated with those effects for signals within the regions.
Pursuant to another aspect of the present invention, there is provided a method for controlling the application of a plurality of image processing operations to a stream of digital image signals. The method operates with respect to a set of predetermined, non-overlapping tile boundaries by selectively controlling the utilization of hardware components through which the signals pass.